We have had occasion to make use of these elements for the
graduation of galvanometers, and, after ascertaining the constancy of the
discharge, have found that the internal resistance of each couple is
nearly 0.175 ohm, with an electro-motive force of two volts. As may be
seen, these elements should, in general, all be mounted for tension, as
they are in the figure, inasmuch as the mobility of the zincs permits,
according to circumstances, of employing a variable number of them without
changing anything. Moreover, with zincs amalgamated in a special manner,
the attack is imperceptible, and the work in open circuit need scarcely to
be taken into consideration.
Yet, despite the qualities inherent to the arrangement that we have just
described, that defect common to all bichromate of potash piles--the
deposit of oxide of chromium upon the carbon--is not here avoided. It
occurs quite slowly, to be sure, but it does occur, and, from this point
of view, the arrangement shown in Fig. 2 is preferable. The elements here
are composed of prismatic porcelain vessels containing, as before, the
solution and porous vessel.
[Illustration: Fig. 3.--COURTOT'S ARRANGEMENT OF THE BICHROMATE PILE.]
The whole is covered with a sheet of ebonite connected with the zinc and
the two carbon plates in such a way that when the pile is not in operation
the whole can be lifted from the liquid.
Pages:
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61